The present invention relates generally to centrifugal compressors and, more specifically, to a method and apparatus for balancing a pressure differential across a bearing.
Turbines may use the exhaust gasses discharged from internal combustion engines as a motive gas to rotate a turbine wheel that may be mounted on one end of a shaft. An impeller may be mounted on the other end of the shaft, and is turned by the turbine wheel to compress gas, which then may be communicated to the engine, thereby supplying charge gas to the engine for increasing engine performance. To improve operating efficiency and to extend range or operation, it may be desirable to control the flow of gasses and control pressure drop across a bearing.
Aircraft, spacecraft, military vehicles, and other vehicles depend upon auxiliary systems, such as pneumatic equipment for pressurizing tanks, transferring fuel (e.g., refueling operations), generating vacuum (e.g., sanitation systems), and other processes. The bearings in a compressor apparatus require sufficient lubrication for smooth operation and longer bearing life. The volumetric gas flow passing through a centrifugal compressor creates a pressure differential across the compressor apparatus that may cause a pressure drop across the bearings, causing lubricant to leak from the bearing and premature bearing failure.
To counteract the aerodynamic pressure differential developed by the centrifugal compressor impeller a fluid channel may be used on the downstream side of the impeller. Leaking lubricant may leak into the fluid channel. Labyrinth seals have been used to attempt to prevent leaking oil from leaving the bearing housing. However, these labyrinth seals have needed to be pressurized and intricate in design to be effective. Pressurizing the labyrinth seal requires additional hardware and design changes to account for diverted gas flow and power requirements.
As can be seen, there is a need for an improved apparatus and method for controlling the leakage of bearing lubricant to provide for longer bearing life without excessive expense or extensive additional hardware.